This invention relates to the lining of pipelines and passageways wherein a flexible tubular liner is everted into and along the pipeline or passageway. The flexible tubular liner includes a curable synthetic resin material such as an epoxy, a polyester, or a phenolic resin and wherein the resin is caused to cure after the flexible tubular lining has been inflated by fluid pressure against the surface to be lined. The fluid pressure may be applied by any suitable medium such as a gas, vapour or liquid or any combination thereof. When the resin cures, the initially flexible lining forms a hard rigid pipe on the pipeline or passageway surface. The resulting pipe may be free standing, or when it is of relatively small thickness, it may form a coating bonded to the pipeline or passageway surface.
Lining methods as described are known, and were first proposed in U.S. Pat. No. 4,064,211. In the method adopted in said U.S. patent, the curing of the synthetic resin is effected by circulating hot water through the inflated lining and the heat in the water effects curing of the synthetic resin. The trouble with heat curing of the resin is that on the one hand curing takes a long time, and on the other hand the resin which was used namely a polyester resin, was in a formulation such that the resin has a relatively short pot life after mixing with a catalyst for the resin.
More recently, attention has been given to the creation and utilization of "latent" resin systems which are systems having a long pot life e.g. measured in terms of months rather than days, as is the case with polyester, but which latent resin systems can be activated in order to cause them to cure by the application of an appropriate activating influence. The activating influence may comprise for example ultrasonic vibrations, or electromagnetic radiation, or light cure, the resin system being appropriately formulated to be activated by these means.
In the prior U.S. patent furthermore the lining tube is provided with a carrier material typically a polyester felt which is impregnated with the resin, and serves to carry the resin and keep it evenly distributed throughout the circumferential length of the lining tube, but more recently, proposals have been made for providing that the resin (with fibrous reinforcement therein if required) is contained between a pair of films so that a fibrous felt may not be necessary.
Additionally, the means suggested for the curing of latent resin systems in lining tubes has been the passage of said means through the tube, after it has been inflated.